Patent Application
20240369061
The present invention relates to a rotary piston compressor for compressing gas, in particular carbon dioxide, wherein the rotary piston compressor has a working housing and a rotary piston, and the working housing has a housing side wall and two housing covers arranged on oppositely situated sides of the housing side wall, wherein a side wall face of the housing side wall and a respective planar sealing face of the respective housing cover enclose a working chamber arranged in the working housing and the rotary piston is rotatably mounted in the working chamber on an eccentric and the rotary piston compressor has a gas inlet for introducing the gas to be compressed into the working chamber and a gas outlet with a pressure-relief outlet valve for discharging the compressed gas from the working chamber, wherein the rotary piston has two piston bases, which face toward a respective one of the planar sealing faces of the housing covers, and a piston lateral surface which faces toward the side wall face of the housing side wall, and a respective planar-seal receiving channel is formed in the piston bases and a planar seal is arranged in each of the planar-seal receiving channels, wherein the planar seals each have a seal surface for contacting one of the planar sealing faces of the housing covers.
Rotary piston compressors per se have been known for quite some time. They are disclosed, for example, in U.S. Pat. No. 4,105,375 and U.S. Pat. No. 4,118,157.
A rotary piston of a rotary piston compressor of the type in question is disclosed in WO 2020/159394 A1. In the technology disclosed in this document, spring elements are arranged in the planar-seal receiving channels in order to press the planar seals against the respective planar sealing faces of the housing covers of the working housing. In practice, generally these springs generate only small pressing forces and usually serve only for keeping contact with the planar sealing faces. In the prior art, the actual sealing effect is usually generated by a gas pressure acting on the seal, wherein, in the prior art, the gas generating the gas pressure reaches the planar seal via gap sizes between the planar sealing faces of the housing covers and the piston bases.
Here, an object of the invention is to provide an improvement which ensures a good sealing effect by means of the planar seals in particular even in the event of relatively high gas pressures in the working chamber.
To achieve this object, the invention takes a rotary piston compressor of the type in question as a starting point to provide that, to press the seal surface of the respective planar seal against the respective planar sealing face, in the piston lateral surface of the rotary piston there are formed lateral-surface openings, which have a pressure-transmitting connection to the respective planar-seal receiving channel via pressure leadthrough lines, which are formed inside the rotary piston and each open into the respective planar-seal receiving channel on a side of the respective planar seal that faces away from the seal surface.
Thus, in the case of the invention, it is no longer provided that the gas pressure reaches the planar seal via gap sizes. Instead, the invention provides that selectively provided in the piston lateral surface are lateral-surface openings, which have a direct pressure-transmitting connection to the planar-seal receiving channel via pressure leadthrough lines, which are formed inside the rotary piston. The pressurized gas from the working chamber can act directly on the planar seal in the planar-seal receiving channel through the lateral-surface openings and the pressure leadthrough lines opening into the planar-seal receiving channel, in order to press the planar seal against the respective planar sealing face of the respective housing cover.
This solution according to the invention on the one hand has the advantage that fewer parts are required to press the seal surface of the respective planar seal against the respective planar sealing face of the respective housing cover. Thus, the spring elements in the planar-seal receiving channel that are used in the generic prior art mentioned in the introduction can be omitted completely in the case of the invention. Primarily, however, in the case of the invention the respective gas pressure from the region of the working chamber, into which the respective lateral-surface opening of the rotary piston opens, is available in the corresponding region of the planar-seal receiving channel in order to press the seal surface of the respective planar seal against the respective sealing face of the respective housing cover. As a result, the contact pressure is automatically also matched to the pressures currently present in this region of the working chamber. This has proven successful in particular when particularly high pressures are reached in the working chamber when the gas is being compressed by means of the rotary piston compressor according to the invention.
A particularly preferred field of use for rotary piston compressors according to the invention is compressing carbon dioxide, in order to then be able to use the carbon dioxide as environmentally friendly coolant or heating medium in a cooling or heating circuit. Here, working pressures of at least 80 bar, preferably at least 100 bar, must be reached to compress the carbon dioxide, in order that this carbon dioxide can be used as coolant for coolers, air-conditioning systems or as heating medium for heating systems in buildings, heat pumps and the like. In the case of rotary piston compressors according to the invention, this predominantly involves compressing carbon dioxide. However, rotary piston compressors according to the invention can naturally also be used to compress other gases.
In this connection, gas denotes everything which is gaseous under normal conditions, that is at a temperature of 20° C. and a pressure of 1013.25 mbar. When compressing the respective gas by means of a rotary piston compressor according to the invention, the gas, in particular the carbon dioxide, may well be brought into a transcritical or supercritical state in which it is liquid and gaseous at the same time. However, in the course of the description of the present invention, the term “gas” will be adhered to in the sense of linguistic simplification.
In rotary piston compressors according to the invention, the rotary piston is rotatably mounted on an eccentric. It would therefore also be possible to refer to rotary piston compressors according to the invention as rotary piston compressors according to the conversion principle. The rotary piston could also be referred to as revolving piston or simply as rotor. The rotary piston compressor itself could also be referred to as rotary-piston compressing device. The planar seals could also be referred to as piston base seals.
The pressure leadthrough lines in the rotary piston are preferably tubular. They may be in the form for example of a bore or a sequence of bores that open out into one another inside the rotary piston. However, there are also other options for the design of the pressure leadthrough lines in the rotary piston.
In any case, the lateral-surface openings are preferably formed in the piston lateral surface at a distance from the piston bases.
There are various options for producing and arranging the planar seals in the respective planar-seal receiving channel. A first group of solutions, which can be implemented particularly inexpensively, to this end provides that the planar seals are produced directly in the respective planar-seal receiving channels. Thus, a preferred variant provides, for example, that the planar seals are each injected in the respective planar-seal receiving channel in the form of an injection molded part. In other words, in this variant an injection molding process is used to produce the planar seals directly in the planar-seal receiving channel and thus also arrange them there at the same time. Another variant may however also provide that the planar seals are each printed in the respective planar-seal receiving channel as 3D printed part. In this variant, a printing process is therefore used to produce the respective planar seal directly in the planar-seal receiving channel and thus also arrange it there at the same time. Yet another variant provides that the planar seals are each pressed in the respective planar-seal receiving channel in the form of a molded pressed part.
As a deviation from this, however, it is also possible to first of all produce the planar seal and then arrange it in the planar-seal receiving channel after it has been produced. It is thus also possible that the planar seals are each prefabricated in the form of an insert part and inserted as such in the respective planar-seal receiving channel.
Preferred variants of the invention provide that the pressure leadthrough lines are each covered by a cap in the region of their opening into the respective planar-seal receiving channel. The use of corresponding caps to cover the opening of the pressure leadthrough lines into the respective planar-seal receiving channel is particularly favorable when the planar seals are formed, for example, directly in the planar-seal receiving channel by injection molding or 3D printing. The caps may prevent the opening of the pressure leadthrough lines being accidentally closed during the production process for the planar seals. Of course, however, corresponding caps can also be used when the planar seal is prefabricated in each case as insert part and inserted as such in the respective planar-seal receiving channel. It should be noted here that the wording “covering said opening by means of the cap” does not mean that the caps close the respective openings of the pressure leadthrough lines in pressure-tight fashion. The caps are only placed on. With a corresponding gas pressure in the pressure leadthrough lines, the gas can by all means penetrate past the caps into the planar-seal receiving channel, in order to press the seal surface of the planar seals against the respective planar sealing face of the respective housing cover. In other variants, however, the caps can also be omitted.
In the sense of the lowest possible number of parts, preferred variants of the invention provide that the planar seals are intrinsically each formed in one piece in one of the planar-seal receiving channels in one of the piston bases. In other words, in such variants there is then correspondingly always only exactly one planar seal in a planar-seal receiving channel. The planar seal of this planar-seal receiving channel is then correspondingly intrinsically formed in one piece.
In rotary piston compressors according to the invention, it is expediently provided that the side wall face of the housing side wall has a completely or at least partially trochoidal form when viewed in a sectional plane parallel to the planar sealing faces of the housing covers.
The rotary piston preferably has two or more corner regions. Expediently, it is provided here that a respective radial seal for sealing the rotary piston with respect to the side wall face of the housing side wall is arranged in the corner regions. It is in turn particularly preferably provided that the piston bases are each delimited by a boundary line in the region between two respective corner regions of the rotary piston, wherein the boundary lines are each in the form of an envelope of an array of trochoid curves.
In order to press the respective radial seal against the side wall face of the housing side wall, there are various options which can also be combined with one another. Thus, in rotary piston compressors according to the invention, it may for example be provided that a respective elastic element, pointing toward the rotary piston, for pressing the respective radial seal against the side wall face of the housing side wall is integrally molded in one piece on the radial seals. In preferred variants, as an alternative or else in addition to this it is provided that the planar seal is used to press the respective radial seal against the side wall face of the housing side wall. Such variants can then provide that the planar seals each have contact faces for pressing the respective radial seal against the side wall face of the housing side wall. These contact faces of the planar seals may each be in the form of slanted faces and act on corresponding slanted faces of the respective radial seal.
As depicted below in the description of the figures, when gas is compressed by means of rotary piston compressors in the working chamber, different sub-volumes are produced, which are separated from one another by the rotary piston and its corner regions and in which different gas pressures also prevail during operation, and the size of these sub-volumes continuously changes during operation. There are respective sub-volumes of the working chamber into which, depending on the current position of the rotary piston, gas is sucked in, while on another side of the rotary piston the gas is respectively compressed at this point in time. This results in both low-pressure and high-pressure sides on different sides of the rotary piston at the same time. In order to prevent gas flowing through the lateral-surface openings, the pressure leadthrough lines and the planar-seal receiving channels from the respective current high-pressure side into a respective current low pressure side, preferred variants of the invention provide that, in the corner regions of the rotary piston, the planar seals are each sealed on their side facing away from the respective seal surface with respect to the planar-seal receiving channel receiving them. In order to bring about this sealing, it is possible to provide for example that the planar seals have sealing projections, which are arranged in corresponding sealing-projection receptacles in the planar-seal receiving channel, on the side facing away from the seal surface. Thus, regions of the planar-seal receiving channel between two respective adjacent corner regions of the rotary piston can be sealed with respect to respective adjacent regions of the planar-seal receiving channel.
As is known per se for rotary piston compressors, rotary piston compressors according to the invention may also be designed with different transmission ratios. The transmission ratio denotes the ratio of the number of trochoid arcs present for forming the side wall face of the housing side wall to the number of corners of the rotary piston. In rotary piston compressors according to the invention, the transmission ratio is expediently 1:2 or 2:3 or 7:6.
In rotary piston compressors according to the invention, the gas inlet and/or the gas outlet may pass through the housing wall. As an alternative, however, it is also possible that the gas inlet and/or the gas outlet pass(es) through the eccentric. Mixed forms of this are also possible.
The planar seals and/or the possibly present radial seals expediently consist of a polymer or a polymer comprising a dry lubricant and/or comprising reinforcing fibers. Polymers that can be used are for example polyetheretherketone, polyamideimide, polyoxymethylene, polyketone, polyamide or polyethyleneterephthalate. Dry lubricants that can be used are for example polytetrafluoroethylene or molybdenum disulfide. Reinforcing fibers considered are for example glass fibers or carbon fibers.
In preferred variants, the housing side wall and the housing covers each have a main body made of an aluminum alloy or a cast iron. A coating is preferably applied to this main body to form the side wall face of the housing side wall and the planar sealing faces of the housing cover. The coating may be a nickel-phosphorus layer, an aluminum-oxide layer or a dry-film lubricating layer. A combination of at least two of these layers is also possible. These coatings can be applied directly to the main body. However, it is also possible for there to be an open-pore adhesive layer, to which the coating is then applied, on the main body. In the case of a main body made of an aluminum alloy, the adhesive layer may be for example an open-pore aluminum-oxide layer, such as anodized aluminum or uncompressed hard anodized aluminum. Another variant of a substrate or adhesive layer consists in an open-pore, plasma-chemically oxidized aluminum layer. In the case of main bodies made of cast iron, the substrate or adhesive layers may be formed for example by phosphating or sandblasting.
Provided it does not distort the meaning, the terms “one” or “a” used here are to be understood in the sense of “at least one”.
Further features and details of preferred configurations of the invention are explained by way of example in the following description of the figures on the basis of various embodiment variants of the invention. In the figures:
The side wall face 7 of the housing side wall 4 and the two planar sealing faces 8 and 9 of the respective housing covers 5 and 6 enclose the working chamber 10 arranged in the working housing 2. The rotary piston 3 is rotatably mounted on the eccentric 11 in the working chamber 10. In this first exemplary embodiment, the eccentric 11 sits on a drive shaft 30 for conjoint rotation. As can be seen in
In this exemplary embodiment, an external toothing 32 is also connected to the drive shaft 30 for conjoint rotation. This external toothing 32 engages in an internal toothing 33, which is connected to the rotary piston 3 for conjoint rotation. This threaded engagement causes the rotary piston 3 to conjointly rotate in the working chamber 10 when there is corresponding rotation of the connecting journal 31 or drive shaft 33. The rotary piston 3 is rotatably mounted on the eccentric 11 in the working chamber 10.
The drive shaft 30 is rotatably mounted in the working housing 2 via the bearings 34 and the securing ring 36. The bearings 34 may be both ball bearings and plain bearings or the like. In the exemplary embodiment shown, the bearing 34 in the housing cover 5 is a ball bearing and the bearing 34 in the housing cover 6 is a plain bearing. However, this does not have to be the case, of course, and can also be configured differently.
A balance weight 35, which compensates the unbalance resulting from the eccentricity of the rotary piston 3, is mounted on the drive shaft 30 for conjoint rotation below the housing cover 6 and thus outside the working housing 2 In the exemplary embodiment shown, the working housing 2 is surrounded by an outer shell 39 of the rotary piston compressor 1. However, this also does not necessarily have to be the case, of course.
In the case of the rotary piston compressor 1 of this first exemplary embodiment, a gas inlet 12 for introducing the gas to be compressed into the working chamber 10 and also a gas outlet 13 with a pressure-relief outlet valve 14 for discharging the compressed gas from the working chamber 10. As explained below, this can be seen particularly clearly in
The rotary piston 3 has two piston bases 15 and 16 which face one of the planar sealing faces 8 and 9, respectively, of the housing covers 5 and 6 and a piston lateral surface 17 facing toward the side wall face 7 of the housing side wall 4. A respective planar-seal receiving channel 18 is in the piston bases 15 and 16. A planar seal 19 is arranged in each of these planar-seal receiving channels 18, wherein the planar seals 19 each have a seal surface 20 for bearing against one of the planar sealing faces 8 and 9 of the housing covers 5 and 6. This is explained in more detail on the basis of the subsequent figures. According to the invention, what is in any case also provided in the case of the rotary piston compressor 1 of this first exemplary embodiment is that, to press the seal surface 20 of the respective planar seal 19 against the respective planar sealing face 8, 9, in the piston lateral surface 17 of the rotary piston 3 there are formed lateral-surface openings 21, which have a pressure-transmitting connection to the respective planar-seal receiving channel 18 via pressure leadthrough lines 22, which are formed inside the rotary piston 3 and each open into the respective planar-seal receiving channel 18 on a side of the respective planar seal 19 that faces away from the seal surface 20. This is explained below, in particular on the basis of
For the sake of completeness, it should be noted that the internal toothing 33 in the rotary piston 3 of this first embodiment is illustrated in
It can be seen in
As explained in the introduction, the cap 24 can in principle also be omitted. If, however, the planar seal 19 is, as realized here, injected in the planar-seal receiving channel 18 in the form of an injection molded part or printed in the respective planar-seal receiving channel 18 in the form of a 3D printed part, the cap 24 prevents inadvertent closing of the respective opening 23 when the planar seal 19 is being formed or produced.
What can be seen here first of all is how the radial seals 26 bear against the side wall faces 7 of the housing side wall 4 to seal the rotary piston 3. In order to generate the contact pressure necessary for the sealing, here two measures are taken. Firstly, an elastic element 28 facing the rotary piston 3 is integrally molded on the radial seal 26 and presses the radial seal 26 against the side wall face 7 of the housing side wall 4. Secondly, however, the contact faces 57 of the planar seals 19 also press the respective radial seal 26 against the side wall face 7. In
Returning to
As already explained in the introduction, the planar seals 19 and also the radial seals 28 expediently consist of a polymer, preferably comprising a dry lubricant and/or reinforcing fibers. The housing side wall 4 and the housing covers 5 and 6 expediently have a main body made of an aluminum alloy or a cast iron. A coating 29 is expediently formed on the respective main body to form the side wall faces 7 of the housing side wall 4 and of the planar sealing faces 8 and 9 of the housing covers 5 and 6. This is also preferably the case in this first exemplary embodiment. In this respect, reference is made to the explanations already set out in the introduction as regards the details and preferred embodiment variants of such a coating 29.
By contrast to the previously explained exemplary embodiments of rotary piston compressors 1 according to the invention, in this exemplary embodiment it is provided that the eccentric 11 on which the rotary piston 3 is rotatably mounted in the working chamber 10 is not rotated like in the first two exemplary embodiments, but rather is arranged rigidly in the outer shell 39 of the rotary piston compressor 1. In this exemplary embodiment, the rotary piston 3 is rotated together with the working housing 2 and thus together with the housing side wall 4 and the two housing covers 5 and 6 about an axis of rotation 60 extending through the eccentric 11, while the eccentric 11 remains stationary. In order to achieve this, the rotary piston compressor 1 of this third exemplary embodiment has a rotor 52, which is connected by means of screws 37 and nuts 38 to the working housing 2 for conjoint rotation and interacts with a stator 54 rigidly connected to the outer shell 39 of the rotary piston compressor 1. The rotor 53 and the stator 54 form a drive motor, which rotates the working housing 2 with the rotary piston 3 mounted on the eccentric 11 in the working chamber 10 of the working housing 2.
A further difference of the third exemplary embodiment in relation to the two previously explained exemplary embodiments is that the gas inlet 12 and the gas outlet 13 in this third exemplary embodiment pass through the eccentric 11, and not through the housing wall 4 as in the first-explained exemplary embodiments. Correspondingly, flow transfer openings 55 that pass through the piston lateral surface 17 are also provided in the rotary piston 3. The gas can enter the corresponding portions of the working chamber 10 from the gas inlet 12 through these flow transfer openings 55 and from there also be conveyed back out again through the gas outlet 13 in compressed form.
In this third exemplary embodiment, the gas inlets 12 and gas outlets 13 that pass through the eccentric 11 open out into a valve cover 52, which sits on the outside of the outer shell 39 of the rotary piston compressor 1 and guides both the gas inlet 12 and the gas outlet 13 into or out of the rotary piston compressor.
Apart from the differences explained up to now and those yet to be explained below, reference can substantially be made to the description of the first exemplary embodiments. This applies in particular to the type of pressure application according to the invention, the planar seals 19 arranged in the planar-seal receiving channels 18 of the piston bases 15 and 16, for pressing their seal surfaces 20 against the planar sealing faces 8 and 9 of the housing covers 5 and 6.
In the section according to
The inwardly pointing sealing projections 48 that are integrally molded on the planar seals 19 are arranged in the corresponding sealing-projection receiving grooves 50 of the rotary piston 3 in the assembled state. They ensure, as is the case in the other exemplary embodiments, that the planar seals 19 are each sealed, with respect to the planar-seal receiving channel 18 that receives them, in the corner regions 25 of the rotary piston 3 on their side facing away from the respective seal surface 20.
As can be seen particularly clearly in
This application is a 371 National Phase of PCT/AT2021/000015, filed Jul. 14, 2021, which is incorporated herein by reference as if fully set forth.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AT2021/000015 | 7/14/2021 | WO |
